The controversy emerged today at one of London’s biggest local authorities after a councillor formally complained that he was insulted by a colleague in the Bengali language, widely spoken by people from Bangladesh.

One councillor at Tower Hamlet’s council, who cannot be named for legal reasons, was accused of calling colleague Abdal Ullah, a “shurer batcha”, which is translated to mean "Son of a pig".

The comments came during a heated exchange between the pair at a meeting last month, triggering a row within the as the slur is considered extremely offensive to Muslims.

While Cllr Ullah, a Labour councillor, protested at the insult, many English-speaking councillors and other public visitors failed to realise its significance because it was issued in a foreign language.

Some councillors later claimed the issue was widespread and did not just involve trading insults.

It is understood that other members of the public have complained to Town Hall bosses about the use of Bengali during meetings.

It was also suggested that some of the Bengali-speaking councillors have been forced translate for their colleagues.

In a letter to the council's Standards Committee, Councillor Ullah raised concerns about the lack of power to enforce only English being used in council meetings.

“Whilst we may have our differences, councillors should afford one another courtesy in our exchanges rather than resorting to unnecessary and abusive insults,” he wrote.

"In my view the use of Bengali or other languages – other than in translation during public questions or petitions and so on – disrupts the transparency and openness of meeting by preventing some present from understanding the exchanges taking place."

Tonight, Peter Golds, the leader of the council’s Conservative group, said Bengali is was being “used in a very foul manner”.

He added: “At a full council meeting the language should be one that all members of the public should understand.

“It is a very serious problem here that a number of councillors insist on speaking in Bengali.”

"It is not just when they get emotional. It happens a lot. Even when they are travelling in a lift before going into a meeting, they will suddenly begin talking in Bengali.”

Brandon Lewis, the Local Government minister, last night criticised the revelations.

"This is a deeply worrying and divisive move. Council meetings should be held in English,” said the Conservative MP for Great Yarmouth.

"Using foreign languages not only undermines transparency and accountability, but it threatens to promote segregation and harm community cohesion.

"Councils in diverse communities should be encouraging everyone to learn and speak English and not practise the politics of division."